Circuit interrupting device



Nov. 5,' 1946. E. F. KoHL CIRCUIT INTERRUPTING DEVICE Filed May 16, 19425 Sheets-Sheet l I INVENTOR Ev rard F. Kohl lill ATTORNEY NovQ 5, 1946.E. F. KOHL CIRCUIT INTERRUPTINC DEVICE Filed May 16, 1942 3 Sheets-Sheet2 MY E INVENToR Everard' E Kahl BYU W ATroRN'EY y Nov. 5, 1946.

E. E. Kol-M CIRCUIT INTERRUPTING DEVICE Filed May 16A, 1942 3Sheets-Sheet 3 v lNvNToR EV rard Koh/Z ATTORNEY Patented Nov. 5, 1946UNITED STATES PATENT OFFICE 23 Claims.

My invention relates to circuit interrupting devices and moreparticularly to an improved circuit interrupting device or governor forcontrolling the speed of motors or the operation of switches, relays,solenoids, or the like.

Governors which have heretofore been provided for controlling theoperation of motors, and particularly motors of the series type toprevent excessive speed under no load conditions and to permit theproduction of substantially increased power when load is applied, dependupon the making and breaking of mechanical contacts which separate undercentrifugal force to control the speed of the motor by controlling themean value of the load current. In such governors, however, it is notonly necessary to maintain the springs controlling the contacts inproper adjustment to provide proper speed regulation but it is alsonecessary to utilize condensers or other valve means to preventexcessive wear -caused by arcing at the contacts.

It is the aim of the present invention to provide an improved circuitinterrupting device or governor for controlling the speed f motors, orfor establishing or interrupting circuits to auxiliary or associateddevices when a rotatable member or shaft to which the governor isattached attains a predetermined speed. My improved circuit interruptingdevice is characterized by the fact that a liquid to metal contact ismade over a comparatively large surface when the device is at rest or isrotated or revolved at-a comparatively low speed which contact is brokenwhen the device is rotated or revolved above a predetermined speed. Thecontact may therefore be broken without substantial arcing. My improvedcircuit interrupting device is also characterized by the fact that theelectrically conductive liquid which is utilized is also heat conductiveand, consequently, heat developed by the flow of electrical currentwhile electrical contact is established or by back electromotive forcewhen the contact is broken is conducted to the outside atmosphere.

It is therefore an object of my invention to provide an improved circuitinterrupting device including means for interrupting an electricalcircuit when a rotatable member with which the device is associatedattains a predetermined speed.

Another object of my invention is to provide an improved circuitinterrupting device or governor including means for establishing anelectric circuit when the device is at rest or is being revolved orrotated at low speed which circuit is automatically interrupted when thedevice is revolved or rotated at a predetermined high speed.

A further object of my invention is to provide an improved circuitinterrupting device or governor including means for making an electricalcircuit when the device is at rest or is revolved or rotated at lowspeed which circuit is automatically interrupted when the device isrevolved or rotated at a comparatively high speed, including adjustablemeans to regulate the speed at which the circuit is interrupted. v

Another object of myinvention is to provide an improved circuitinterrupting device in which contact for establishing an electricalcircuit is provided by an electrically conductive liquid when the deviceis at rest or is being revolved or rotated at a comparatively low speedand in which the buoyant force of the liquid becomes effective ininterrupting the circuit `when the device is revolved or rotated at acomparatively high speed.

Other objects and advantages of my invention will be apparent as thespecification proceeds.

My invention will be better understood by reference to the accompanyingdrawings in which:

Fig. 1 is an elevational view of my improved circuit interruptingdevice, showing it associated with a disk attached to a motor shaft, afragmentary portion of the motor being shown with parts in section andparts in elevation;

Fig. 2 is a side elevational view of the disk shown in Fig. l with myimproved circuit interrupting device attached thereto and a fragmentaryportion of the housing for the disk and device;

Fig. 3 is a plan view as seen from a plane passing through line 3--3 ofFig. 2, looking in the direction of the arrows with parts broken away toshow underlying structure;

Fig. 4 is a cross sectional View of my improved circuit interruptingdevice, showing the parts in a circuit making position;

Fig. 5 is a view similar to Fig. 4 but showing the parts in a circuitinterrupting position;

Fig. 6 is a side elevational view of a modified form of my improvedcircuit interrupting device mounted to rotate with a driven shaft,showing in cross section a housing for the device and driven shaft;

Fig. 7 is an end view of the apparatus shown in Fig. 6, the carbon brushbeing omitted and the major portion of the housing being broken away toshow adjacent structure;

Fig. 8 is a cross sectional view of the circuit interrupting deviceshown in Figs. 6 and 7 with parts in circuit making position and showingadjacent parts of the shaft and slip ring partly in elevation and partlyin section;

Fig. 9 Ais a view somewhat similar to Fig. 8,

showing the parts of the device in a circuit interrupting position;

Fig. 10 is a wiring diagram of electric circuit in which the circuitinterrupting device shown in Figs. 6 to 9, inclusive, is connected;

Fig. 11 is a cross sectional view oi' a modified form of my improvedcircuit interrupting device taken on the line II-II of Fie. 12, showingthe device attached to a motor shaft and a fragmentary portion of themotor in elevation;

Fig. 12 is an end View of the device shown in Fig. 1l, with parts brokenaway to show adjacent structure;

Fig. 13 is an enlarged detail view of a portion of the device shown inFig. 11,'

Fig. 14 is a cross sectional view or a modified form of the circuitinterrupting device shown in Fig. 11; and

Fig. l5 is a wiringT diagram showing the electrical connections of thecircuit interrupting device illustrated in Fig. 14.

Broadly stated, my improved circuit interrupting device comprises acasing containing an electrically conductive liquid which is adapted toestablish an electrical circuit when the device is at rest or whenrotated or revolved at low speed and which is adapted to interrupt thecircuit when the device is rotated or revolved at high speed. It may,for instance, be associated in any desired manner with a motor tocontrol its speed in which case it acts as a governor, or it may beconnected or associated with a driven shaft and be utilized to establishor interrupt a circuit to an auxiliary device, such as a solenoid,electrical switch, or to another motor when the driven shaft attains apredetermined speed.

Figs. 1 to 5 of the drawings illustrate one form of my improved circuitinterrupting device, Figs. 1 and 2 showing the device associated withand adapted to govern the speed of a motor to be driven and while themotor may be of any desired type, my improved device is particularlyadapted to be utilized to control or govern the supply of current tomotors of the series type which have the tendency to develop exceedinglyhigh speed under no load conditions.

As shown more particularly in Figs. 4 and 5, my improved circuitinterrupting device acts as a switch to form an electrical circuitbetween a casing I and a terminal 2. For this purpose, the casingcontains an electrically conductive liquid 3 which also preferably has ahigh specific gravity, such as mercury. The casing also contains aplunger 4 which fits loosely in the casing and is preferably composed oflight material having a rest or rotated or revolved at low speed bymeans g of a spring 5 disposed between a pair of contacts 6 and 'Iprovided with annular abutments 8 and 9, respectively, which serve tohold the spring in place. When mercury is utilized as the conductiveliquid, the contacts and metal portion of the casing should of course beformed of metals which do not readily amalgamate with mercury.

As illustrated, contact 6 bears against one end of plunger 4 and is ofless peripheral extent than the plunger to provide a space for anannular layer of the conductive liquid and contact I is provided with ashank I0 which extends through a layer of insulating material IIsupported upon and held in place by an annular shoulder I3 and aninturned flange I4 of the casing. Shank IG ii f3 also extends through aflange I5 on terminal 2 and is peened or riveted over flange I5 tomain-- tain the iiange in engagement with insulating layer II. Asillustrated in Fig. 4 it will be noted that current conducted to casingI flows through the mercury to contact 6 and from thence through spring5, contact l, and shank l0 to terminal 2. When the device, however isrotated or revolved about an axis which is normal to the longitudinalaxis of the casing and is closer to the terminal 2 than end I6, theliquid is centrifugally thrown to the end I6 as illustrated in Fig. 5and buoyantly :forces plunger 4 inwardly compressing spring 5 andproviding a chamber at the end of casing I6 to receive the liquid, Sincethe plunger 4 is formed of an electrically insulating material, it willbe apparent that when the mercury is in the position shown in Fig. 5,the circuit between the casing I and terminal 2 is interrupted.

While my improved circuit interrupting device or governor may beassociated with a motor to be driven of any desirable type to controlits speed, or connected to a driven shaft to control the speed oroperation of an associated or auxiliary device, in Figs. 1, 2 and 3 ofthe drawing it is shown connected in the load circuit of a motor Il tobe driven which as shown is provided with an armature shaft I8 rotatablymounted in bearings I9 formed in a tubular extension of motor casing 2|.For the purpose of conducting current from a line to the casing I andtransmitting it to the motor through the circuit interrupting device, adisk 22 formed of a suitable insulating material, such as molded orlaminated material, is affixed to armature shaft I8 by any suitablemeans. As illustrated, a bushing 23 keyed to a reduced portion of theshaft has an annular flange 24 arranged on one side of the disk 22 and awasher 25 is secured rmly against the opposite side by a bolt 2Sthreaded in the end of the shaft.

Disk 22 rotates with the motor shalt and is provided on one side withelectrically conductivev slip rings 2l and 2S, the outer ring 28 beingconnected to disk 22 by suitable means, such as bolts 29 and a bolt 3i!passing through an extension 3| of terminal 2. Slip ring 21 is connectedto disk 22 by means of bolts 32 passing through flanges of a bracket 33formed of a conductive metal which supports and is in electrical contactwith casing I of the current interrupting device and by bolts 34 passingthrough a counterweight 35.

To supply current to the motor through the circuit interrupting device,a carbon brush 35 is slidably arranged in an externally threaded bushing31 which bushing is insulatingly mounted in the cover of a housing 3Bsupported by the motor casing and is electrically connected to lead L1.Brush 36 is held in engagement with slip ring 21 by means of a spring 39interposed between the carbon brush and a cap 4I) threaded on thebushing. A carbon brush 4I provided with a terminal 42 leading t0 themotor is forced against slip ring 28 in a similar manner.

The operation of my improved apparatus will now be apparent. When themotor is at rest or is being rotated at low speed, current supplied tobrush 36 from a suitable source of supply is conducted through bolts 32to the casing i of the circuit interrupting device and from thencethrough the device to terminal 2, conductor 3| and bolt 3!! to carbonbrush 4I, from whence it is conducted to the motor I1 and back to thesource oi supply. When the motor speed increases beyond a preedetermined amount, however, such as when the load is reduced, theelectrically conductive liquid is thrown by centrifugal force to the endI6 of the casing and buoyantly forces plunger 4 inwardly, thusinterrupting the supply of current to the motor. In view of the largecontact area between the mercury and contact 6, it will be apparent thatno sparking will occur when the current is interrupted and any mercurythat is vaporized will be quickly condensed. Any heat developed willalso be conducted through the mercury to the outside atmosphere. Whenthe motor slows down to the desired extent, spring 5 overcomes thebuoyant force of the mercury and electrical contact is again made. Itwill therefore be apparent that the motor may be maintained at almost aconstant predetermined speed, irrespective of the load, the speeddepending upon the force of spring 5.

Another form of my improved circuit interrupting device or governor isshown in Figs. 6 to 9, inclusive, and while a circuit interruptingdevice of this type may be utilized to control or govern the supply ofcurrent to a motor in the same manner as the apparatus illustrated inFigs. l to 5, in which case the speed at which the circuit is broken isadjustable, as illustrated, the device is attached to a driven shaft 49.The circuit interrupting device comprises a casing having a closed end5l which contains an electrically conductive liquid 52, such as mercury,a movable plunger 53 formed of light material having a high electricaland heat resistance, such as lava, and a `contact 54 which is normallyheld in engagement with plunger 53 by a spring 55 interposed betweencontact 54 and a plug 56 formed of a molded insulating material, such asasbestos or wood ilour bound together by a phenolic condensationproduct, which is threaded into the open end of the casing. As shown,the spring is held in place by abutments 51 and 58 extending fromcontact 54 and plug 56, respectively, and a conductor 59 extends fromcontact 54 through and beyond plug 56 and forms a terminal 60 to which asuitable conductor may be attached.

As illustrated in Fig. 8 when current is conducted to casing 5I, itpasses through the mercury 52 to contact 54 and from thence throughconductor 59 to terminal 60. When shaft 49, however, is rotated at acomparatively high speed, the mercury is centrifugally thrown toy theend 5| of casing 59 and buoyantly forces plunger 53 inwardly against theforce of spring 55, breaking the contact, The rotative speed of thedriven shaft at which the mercury in casing 59 forces plunger 53inwardly is determined by the compression of spring 55 which may bevaried by the extent to which plunger 55 is threaded into the casing andfor this purpose plug 56 is provided with an angular head 6I which maybe readily engaged by a suitable tool for adjusting the position of theplug.

In Figs. 6 to 9 of the drawings, means are shown associated with thecircuit interrupting device for supplying current to an auxiliarydevice, such as a solenoid, relay or a, motor, when the driven shaft isat rest or rotating at a low speed and for interrupting the supply ofcurrent to the auxiliary device when the driven shaft attains apredetermined speed. For this purpose, the shaft 49 is provided with ahousing 62 having a removable cap 53 which housing forms a chamber forthe device, a slip ring, 64, and a carbon brush having a terminal 66electrically connected to the brush outside the housing.

Slip ring E4 is connected to the shaft by a iiber pin 61 and is providedwith an extension 68 to which a conductor 69 is secured by any suitablemeans, such as screw 10, the other end of conductor 69 being secured toterminal 60. The carbon brush 65 is slidably mounted in a, threadedbushing 'll and is held in engagement with slip ring 64 by a spring 12interposed between the brush and a cap 13 threadingly mounted in thebushing.

While the circuit interrupting device disclosed in Figs. 6 to 9,inclusive, may be utilized to control any electrically operated deviceassociated with the governor, such as switches, relays, motors or thelike, as illustrated diagrammatically in Fig. 10, it is shown associatedwith a solenoid which is adapted to be deenergized when the driven shaftattains a predetermined speed. As illustrated more particularly in Figs.6 and 10, current is supplied to the casing 58 of the circuitinterrupting device from line Li and when the device is in the positionshown in Fig. 8, the

current passes from the casing through conductors 59 and 59, slip ring64, carbon brush 65 and conductor 55 to solenoid l5 and from solenoid 15through conductor 16 to line L2. When the shaft, however, is rotatedabove a predetermined speed,

the circuit to solenoid l5 is interrupted. The

deenergization of the solenoid may of course be utilized to actuate aswitch to open or close the current supply to apparatus of any desiredtype. When mercury is utilized as the conductive liquid, the contactsand other metal parts should of course be formed of conductive metalwhich does not amalgamate with mercury,

Figs. ll. to 13 of the drawings illustrate another form of my improvedcircuit interrupting device, which as shown, acts as a governor forcontrolling the supply of current to Aa motor although obviously thedevice may be associated with a driven shaft and may be utilized toestablish or interrupt an electric circuit to an auxiliary device in themanner shown in Figs. 6 to 10. As illustrated, the circuit interruptingdevice comprises a casing, including a side 8D having a central hub 8|bored to receive the shaft 82 of a motor 83 and a peripheral portion 84which terminates in an upstanding flange 85 to which is secured a cover86 having an outwardly extending offset portion 8l which terminates inan annular ilange 88 providing a central opening. The cover may besecured to the body portion by suitable means, such as by Welding, or toprovide ease of assembly by bolts 89, which as shown extend through thecover and flange 85. Although it is not essential, the cover may also beprovided with a peripheral flange 90 in telescopic engagement withperipheral portion 84, and a plurality of inwardly extending lugs 9| forpurposes to be subsequently described.

As in previous modiiications, means are provided for establishing acircuit between a conductive liquid, such as mercury, and a metalcontact to establish an electric circuit when a rotatable member withwhich the device is associated is at rest or is rotated at low speed,which circuit is adapted to be interrupted when the rotatable memberattains a predetermined speed. For this purpose, a sleeve 9m formed ofelectrical insulating material is mounted upon a bearing 92 surroundingshaft 82 and is prevented from rotating therewith by means of a. setscrew extending through a tubular extension 93 of the bell ring of themotor into a recess formed in the sleeve. Sleeve 9Ia extentk through thecentral opening in cover 86 and terminates within the casing in anenlarged portion 94 having annular recesses to receive contacts 95 and95a.

As illustrated, hub 8| is secured to shaft 82 and the casing contains anelectrically conductive liquidl such as mercury which, as shown, ispresent in an amount suflicient to bridge contacts 95 and 95a when themotor is at rest or is rotating at low speed to establish a circuitbetween a conductor 96 leading from a suitable source of electricalenergy to contact 95 and a conductor 91 connected to contact 95a andleading to motor 83 and from thence back to the source of supply. Theconductors may be connected to the contacts in any suitable manner. Asillustrated, they are molded in insulating sleeve9la.

To control the speed of the motor, means are provided to interrupt thesupply of current to the motor when it rotates above a predeterminedspeed. For this purpose, an adjustable member 98 having a conicalportion inclined upwardly within the casing and a base 99 is secured toside portion 80 by a plurality of bolts |00 threaded into the sideportion and the base, each of which is provided with a compressionspring |02 interposed between its head |0| and side portion 80, and aplurality of segmental blocks |03 are arranged between the conicalportion o1 the adjustable member and the periphery of the ca.,- ing,each of which has an inner portion |04 having the same degree ofinclination as the conica1 portion of the adjustable member. When themotor is at rest or is rotating at low speed7 springs |02 maintain base99 in engagement with side portion 80 and segmental blocks |03 inengagement with the inner periphery of the casing. Segmental blocks I 03are spaced sufficiently from each other to permit radial movement butotherwise substantially ll the chamber between the conical portion ofadjustable member 93 and the inner periphery of the casing, andconsequently only a small amount of mercury is present in this chamberwhen the motor is at rest or is rotating at low speeds while suicientmercury is present in chamber 81a formed by offset portion 81 to bridgethe contacts.

When armature shaft 82 is rotated at a predetermined speed, however,depending upon the compression of springs |02, the mercury seeps betweencover 8S and segmental blocks |03 and forms an annulus around the innerperiphery of the casing which buoys blocks |03 radially inwardly with aforce depending upon the rotative speed of the motor and the depth towhich the segmental blocks are immersed. The inward movement of blocks|03 in turn forces adjustable member 58 axially inwardly providing achamber between segmental blocks |03 and the inner periphery of thecasing to which the mercury iiows from chamber 81a, thereby interruptingthe circuit to the motor. When the rotative speed. of the shaftdecreases to a predetermined extent, springs |02 move adjustable member93 to the position shown in Fig. 11, forcing segmental blocks |03outwardly against the inner periphery of the casing, thereby displacingthe mercury which flows back into chamber 01a and again establishes acircuit to the motor. The rotative speed of the armature shaft at whichthe circuit is broken is of course dependent upon the amount and type ofconductive liquid which is utilized, the composition of segmental blocks|03, and the compression of springs |02. When a predetermined amount ofa liquid, such as mercury, is utilized and the segmental blocks areformed of light molded material, the speed at which the circuit isinterrupted may be varied by adjusting bolts |00 to vary the compressionof springs |02. When mercury is utilized as the conductive liquid, thecontacts should be formed of a metal that does not readily amalgamatewith mercury, such as platinum or tungsten. Lugs SI may be provided forrotating segmental blocks |03 with the casing although they are notessential.

The apparatus disclosed in Fig. 14 is similar to that shown in Figs. 11to 13 with the exception that means independent of springs |02 are alsoprovided to vary the speed at which the circuit to the motor isinterrupted. For this purpose, contact 95 is arranged in the outerrecess of sleeve 9|a as illustrated in Fig. 11 to which conductor 96 isconnected, and contacts 05a, 95h, 95o and 95d, are arranged in spacedrelation to contact 95 and to each. other and are disposed in additionalrccesses formed in the sleeve. The distance of the outer periphery ofcontacts 95a, 95h, 05e and 95d to the inner periphery of chamber 31avaries in accordance with their distance from contact 0:5, the outer'periphery of contact 95 being closest to the inner periphery of thecasing, and the outer periphery of contact 95d being the most remote. Asshown diagrammatically in Fig. l5, conductors 91, 97a, Gib and 81e lead,respectively, from contacts 95d, 95h, 95o and 95d to a switch |05 whichis connected to the inlet terminal of the motor by conductor |05, theoutlet terminal of the motor being connected by a conductor |07 to lineL2.

The operation of the circuit interrupting device or governor shown inFig. 14 is similar to that shown in Fig. 11 but the interruption of thecircuit to the motor will take place at speeds depending upon thesetting of switch |05. For instance, if switch |05 is set to connectconductor 97e leading to Contact 95d in circuit with conductor 95leading to contact 95, as shown, it will be apparent that the circuitwill be interrupted `at a lower speed than when the switch is connectedto conductor 91D leading to Contact 95o. In a like manner, it willrequire a higher speed to interrupt the circuit when switch |05 isconnected through conductor 97a to contact 95!) than when it isconnected to contact 915e, the highest speed at which interruption takesplace being attained when switch Hic is connected through conductor 91with contact 95d. It will thus be seen that by the arrangement shown inFig. 14, the speed at which the circuit to the motor is interrupted maybe varied according to the setting of switch |05 and may also beadditionally varied by the compression of springs |02 as explained inconnection with the description of Figs. 11 to 13.

In the modifications shown in Figs. 1l to 13, inclusive, and Figs. 14and l5, it will be noted that the chamber containing segmentai blocks|03 has a considerably larger diameter than chamber Bla containing thecontact discs and consequently a very slight displacement of segments|03 produces a relatively large displacement of the electricallyconductive liquid. The electric circuit will therefore be quicklyinterrupted when motor shaft 02 rotates above the desired speed andquickly established when the motor falls below the desired speed. Myimproved device is therefore sensitive in servico.

What I claim is:

1. Apparatus of the class described compris'- ing a casing containing anelectrically conductive liquid, a plunger formed of an electricalinsulating material slidably mounted in said casing, a contact engagingsaid plunger, said contact being spaced from said casing and being inelectric circuit with said liquid when the casing is at rest and saidplunger being displaceable by the centrifugally developedbuoyant forceof said liquid to interrupt said circuit when said casing is moved at apredetermined speed about an axis of said casing.

2. Apparatus of the class described comprising an electricallyconductive casing containing an electrically conductive liquid, aterminal insulated from said casing, a plunger formed of electricalinsulating material slidable in said casing, a contact spaced from saidcasing and supported by said plunger, resilient means engaging saidcontact and in electric circuit with said terminal forV maintaining saidplunger at one end of said casing, said Contact being normally inelectric circuit with'said liquid and said plunger being displaceable bythe centrifugally developed buoyant force of the liquid to break thecircuit between said liquid and contact.

3; Apparatus of the class described comprising a casing having a closedend portion and containing an electrically conductive liquid, a plungerformed of an electrically insulating material slidable in said casing, acontact supported on said plunger and in electrical circuit with saidliquid when the casing is at rest and the outer periphery of which isspaced from said casing, resilient means for maintaining said plunger inengagement with the end portion oi said casing, and said casing beingmovable to centriiugally throw said liquid to the end portion of saidcasing to buoyantly displace said plunger and said Contact from saidliquid to interrupt said circuit.

4. Apparatus of the class described comprising a casing containing anelectrically conductive liquid, a contact arranged in but spaced fromsaid casing, means for normally maintaining said contact in electricalcircuit with said liquid, said contact being displaceable to break saidcircuit by the centrifugally-developed buoyant force of said liquid, andmeans for adjustingl said maintaining means to vary the force requiredto displace said contact.

5. Apparatus of the class described comprising a casing containing anelectrically conductive liquid, a contact arranged in but spaced fromsaid casing, resilient means for normally maintaining said contact inelectrical circuit with said liquid, said liquid being centrifugallyseparable from said contact, and means for adjusting said maintainingmeans to vary the centrifugal force required to displace said liquid.

6. Apparatus of the class described comprising a casing having a closedend portion containing an electrically conductive liquid, a plungerformed of electrically insulating material slidable in said casing, acontact supported on said plunger, means for maintaining said plungeragainst the closed end of said casing, and means for revolving saidcasing about an axis spaced from the closed end portion at suicientspeed to centrifugally throw the liquid to the closed end portion ofsaid casing and the centrifugally developed buoyant force of the liquidbeing adapted to move said plunger and displace said contact from saidliquid.

7. Apparatus of the class described comprising a casing having a closedend portion containing an electrically conductive liquid, a plungerformed of electrically insulating material slidable in said casing, acontact supported on said plunger, resilient means engaging said contactfor normally maintaining said plunger 10 at the end of said casing,means for rotating said casing at suiicent speed about an axis tocentrifugally throw said liquid to the end of said casing to buoyantlymove said plunger and displace'said contact from the liquid, and meansfor adusting the tension on said resilient means to vary the speed atwhich said liquid is capable or displacing said plunger.

8. Apparatus of the class described comprising a casing containing aconductive liquid, an electrically conductive contact in electricalcircuit with said liquid when said casing is at rest, and a displaceableelement arranged Within said casing and movable by thecentrifugally-developed buoyant force of said liquid for interruptingsaid circuit when said casing is moved at a predetermined speed aboutone of its axes.

9. Apparatus of the class described comprising a casing containing aconductive liquid, a contact in electrical circuit with said liquid whensaid casing is at rest or is moved about one of its axes at low speed,means arranged within said casing and movable by the centrifugallydeveloped buoyant force of said liquid for interrupting said circuitwhen said casing is moved at a predetermined speed about said axis, andresilient means for maintaining said contact in electric circuit withsaid liquid until said casing attains its predetermined speed.

10. Apparatus of the class described comprising a casing containing aconductive liquid, a contact in electrical circuit With said liquid whensaid casing is at rest, means arranged within said casing and movable bythe centrifugallydeveloped buoyant force of said liquid for interruptingsaid circuit when said casing is moved at a predetermined speed aboutone of its axes, and adjustable means for maintaining said contact inelectric circuit with said liquid until said casing attains itspredetermined speed.

11. Apparatus of the class described comprising a casing containing aconductive liquid, a contact in electrical circuit with said liquid whensaid casing is at rest, means arranged Within said casing and movable bythe centrifugallydeveloped buoyant force of said liquid for interruptingsaid circuit when said casing is moved at a predetermined speed aboutone of its axes, and adjustable resilient means for maintaining saidcontact in electric circuit with said liquid until said casing attainsits predetermined speed.

12. Apparatus of the class described comprising a casing containing anelectrically conductive liquid, an electrically conductive contactarranged in said casing, reslient means for maintaining said contact inelectrical circuit with said liquid When said casing is at rest o1 ismoved about one of its axes at low speed, and said liquid beingcentrifugally separable from said contact when said casing is movedabout said axes at suicient speed to cause the liquid to overcome theforce of said resilient means.

13. Apparatus of the class described comprising a metallic casingcontaining an electrically.v

conductive liquid, an electrically conductive'contact of substantallydisc shape having its outer peripheral portion spaced from but arrangedin proximity to said casing and said liquid being in bridging relationwith the entire outer periphery of said contact and with the innerportion of said conductive casing to form an electrical circuit betweensaid casing and said contact over a comparatively large area, and saidcasing being movable about one of its axes to centrifugall displace saidliquid from said contact. f

14. Apparatus of the class described comprising a cylindrical metalliccasing having a closed end and containing an electrically conductiveliquid, a cylindrical plunger formed of electrical insulating materialslidably mounted in said cas-l ing with its outer periphery arranged inproximity to the walls of said casing but spaced suillciently therefromto form a chamber for a narrow annulus of the conductive liquid betweensaid plunger and said casing, a contact of substantially disc shapesupported on said plunger and having its outer periphery spaced fromsaid casing but in close proximity thereto, said casing and contactbeing bridged by said liquid when said casing is at rest, and saidcasing being movable about one of its axes to centrifugally force theliquid to the closed end of the casing to interrupt the circuit betweensaid casing and contact.

15. Apparatus of the class described comprising a rotatable shaft, acasing containing a conductive liquid associated with and adapted to bedriven by said shaft, an electrically conductive contact in circuit withsaid liquid when said shaft is at rest, and a displaceable elementarranged within the casing and movable by the centrifugally-developedbuoyant force of sai liquid for interrupting said circuit when saidshaft is rotated at a predeterminedv speed.

16. Apparatus of the class described comprising a shaft, a casingmounted on said shaft and rotatable therewith, said casing containing aconductive liquid and having a contact chamber and an enlarged segmentchamber, a pair of electrically conductive contacts arranged within thecontact chamber which are bridged by said liquid to form an electriccircuit when the casing is at rest or is being rotated at low speed anda plurality of segments maintained in engagement with the innerperiphery of the segment chamber when said shaft is at rest, and meansfor rotating said shaft, said liquid being thown outwardly bycentrifugal force to buoyantly force said segments radially inwardly toform a space for said liquid in the segment chamber to thereby interruptsaid circuit when said shaft is rotated above a predetermined speed.

17. Apparatus of the class described comprising a movable casingcontaining a conductive liquid and being shaped to provide a contactchamber communicating with a second chamber of greater peripheral extentthan the contact chamber, an electrically conductive contact arranged inthe contact chamber which is in electrical circuit with said liquid whensaid casing is at rest, and means arranged in the second chamber anddisplaceable by the centrifugally-developed buoyant force of said liquidto provide a space in the second chamber for said liquid when saidcasing is moved about one of its axes at a predetermined speed tothereby interrupt the circuit between the contact and said liquid.

18. Apparatus of the class described comprising a. casing containing aconductive liquid, said casing being shaped to provide a Contact chamberand a second communicating chamber ol greater peripheral extent than thecontact chamber, a pair of electrically conductive contacts arranged inthe contact chamber which are in electrical circuit with said liquid andeach other when the casing is at rest, movable means arranged in thesecond chamber, adjustable resilient means for maintaining the movablemeans at the inner periphery of the casing forming the second chamberwhen the casing is at rest, and said casing being movable about one ofits axes to centrifugally throw said liquid into the second chamber andforce the movable means radially inwardly against the force of theresilient means to provide a space for the liquid in the second chamber,thereby interrupting the circuit between the contacts and said liquid.

19. Apparatus of the class described comprising a casing containingmercury, an electrically conductive contact in circuit with said mercurywhen said casing is at rest, and a displaceable element arranged withinsaid casing having a lower specic gravity than the mercury which ismovable by the centrifugally-developed buoyant force of said mercury forinterrupting said circuit when said casing is moved at a predeterminedspeed about one of its axes.

20. Apparatus of the class described comprising a rotatable casingcontaining an electrically conductive liquid, a pair of contactsarranged in but spaced from said casing, said contacts being inelectrical circuit with said liquid when the casing is at rest or isbeing rotated at low speed and at least one of said contacts beingspaced from said liquid to interrupt the circuit when the casing isrotated at a predetermined speed, and resilient means for preventinginterruption of said circuit until the casing has acquired itspredetermined speed.

21. Apparatus of the class described comprising a rotatable casingcontaining an electrically conductive liquid, a pair of contactsarranged in but spaced from said casing, said contacts being inelectrical circuit with said liquid when the casing is at rest or isbeing rotated at low speed and at least one of said contacts beingspaced from said liquid to interrupt the circuit when the casing isrotated at a predetermined speed, and adjustable means for preventinginterruption of said circuit until the casing has acquired itspredetermined speed.

22. Apparatus of the class described comprising a rotatable casingcontaining an electrically conductive liquid, a pair of contactsarranged in but spaced from said casing, said contacts being inelectrical circuit with said liquid when the casing is at rest or isbeing rotated at low speed and at least one of said contacts beingspaced from said liquid to interrupt the circuit when .1; the casing isrotated at a predetermined speed,

and adjustable resilient means for preventing interruption of saidcircuit until the casing has acquired its predetermined speed.

23. Apparatus of the class described comprising a casing containing aconductive liquid and said casing being rotatable about its axis tocentriiugally displace the liquid from the contact chamber into thesecond communicating chamber, a plurality of electrically conductivecontacts arranged in the contact chamber including a main contact havingits outer periphery spaced from the inner periphery of said casing and aplurality of auxiliary contacts spaced from each other and the maincontact, and the distance of the outer periphery of each of saidauxiliary contacts from the inner periphery of the casing being greaterthan the main contact and being variable with respect to each other andsaid contacts being bridged by said liquid when said casing is at rest.

EVERARD F. KOI-IL.

